May be the governments will deal only with dApps (smart contracts) that they consider “illegal”, but not the Ethereum platform itself? Just like some crypto exchanges not allowed to operate in US, or US citizen are prevented to participate in ICO etc. This can’t be that bad, can it?

Hold on though. Some governments do regulate their country's internet. China sensors all sorts of connections. For example, use of TOR is illegal, and connection to a known TOR node is prevented (I believe it's done through ISP monitoring, though that's just a guess). Use of blockchains could also potentially be prevented in the same way.
I think the best way to go about keeping crypto legal (for those of us in democracies) is to get involved in getting benevolent, unregulatory politicians into power.